Add test for final class

java/ql/test/utils/model-generator/CaptureSummaryModels.expected

@@ -1 +1,2 @@
+| p;FinalClass;false;returnsInput;(String);;Argument[0];ReturnValue;taint; |
 | p;FluentAPI;false;returnsThis;(String);;Argument[-1];ReturnValue;value; |

java/ql/test/utils/model-generator/p/FinalClass.java

@@ -0,0 +1,15 @@
+package p;
+
+public final class FinalClass {
+
+    private static final String C = "constant";
+
+    public String returnsInput(String input) {
+        return input;
+    }
+
+    public String returnsConstant() {
+        return C;
+    }
+
+}